A major goal of this research is to continue with the characterization of the protein of isolated and purified photoreceptor complexes and reaction center complexes prepared from photosynthetic bacteria, particularly those from R. rubrum. In the coming year, we plan to begin determination of the amino acid sequence of one of the major polypeptides which we have isolated in large quantities in pure form from R. rubrum. We will also look for isolation procedures to purify large quantities of the other polypeptide of the photoreceptor complex. Our analytical work to clarify the role of ubiquinone will be continued by extending the radioactive assay and extraction technique to Chromatium and R. spheroides. Together with this probing of the role of ubiquinone we will also attempt to selectively remove nonheme iron from in vivo systems to gain further insight on its role. Reconstitution of activity experiments will be conducted at two levels: 1) Generation of a photoreceptor complex from the purified components (pigments, polypeptides, ubiquinone, etc.). 2) Restoration of photophosphorylation activity to selectively depleted chromatophores. BIBLIOGRAPHIC REFERENCES: "Free Radicals in Photosynthesis" P.A. Loach and B.J. Hales, in Free Radicals in Biology, Ed. W.A. Pryor, Academic Press, N.Y., Ch. 5 (1976). "Chemical Properties of the Phototrap in Bacterial Photosynthesis", P.A. Loach, Ch. 2, in Vol. 4 of Progress in Bioorganic Chemistry, Wiley Interscience, 89 (1976).